title: Genomic organization and functional characterization of the chemokine receptor CXCR4, a major entry co-receptor for human immunodeficiency virus type 1.
abstract: CXCR4 is both a chemokine receptor and entry co-receptor for T-cell line-adapted human immunodeficiency virus type 1. The genomic organization and promoter function for the entire transcription unit of CXCR4 were determined. The gene contains 2 exons of 103 and 1563 base pairs (bp) interrupted by a 2132-bp intron precisely between codons 5 and 6 of the coding sequences. A transcription start site was identified 88 bp upstream of the initiation codon, and a polyadenylate addition site was identified 22 bp 3' to a polyadenylation signal. Transient expression assays defined a minimal promoter at positions -114 to +43 relative to the transcription start site. This region contains a TATA box, a nuclear respiratory factor-1 (NRF-1) site, and two GC boxes. Specific factor binding to the NRF-1 site and GC boxes were demonstrated by gel mobility shifts and DNase I footprinting. Site-directed mutagenesis showed that the NRF-1 site is crucial for promoter activity providing the first evidence for the regulation of a signal transduction gene by NRF-1. Sequences between -691 and -191 repress CXCR4 promoter activity. Further study of these regulatory elements will be important to understanding how CXCR4 functions as both a chemokine receptor and human immunodeficiency virus type 1 entry co-receptor.
authors.affiliation: Division of Retrovirology, Walter Reed Army Institute of Research, Rockville, Maryland 20850, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Wegner
authors.forename: P K
authors.initials: PK
authors.lastname: Ehrenberg
authors.forename: G
authors.initials: G
authors.lastname: Chang
authors.forename: D E
authors.initials: DE
authors.lastname: Dayhoff
authors.forename: A L
authors.initials: AL
authors.lastname: Sleeker
authors.forename: N L
authors.initials: NL
authors.lastname: Michael
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D018983:DNA Footprinting; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D051265:NF-E2-Related Factor 1; D051266:Nuclear Respiratory Factor 1; D051264:Nuclear Respiratory Factors; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D019718:Receptors, CXCR4 / Q000235:genetics* / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013728:Terminator Regions, Genetic; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051265:NF-E2-Related Factor 1; C495633:NRF1 protein, human; D051266:Nuclear Respiratory Factor 1; D051264:Nuclear Respiratory Factors; D019718:Receptors, CXCR4; D016329:Sp1 Transcription Factor; D015534:Trans-Activators